Chapter 9: Bioprocessing of Cost-competitive Biobased Organic Acids

A major challenge to producing cost-competitive biobased organic acids is the high cost of product recovery from the bioreactor due to the low product titers that are achievable in state-of-the-art bioconversion processes. A new approach in bioprocessing that integrates upstream bioconversion and downstream product separation into a continuous process, called a separative bioreactor (SB), is described. Incorporating an innovative membrane technology, resin wafer electrodeionization (RW-EDI), with SB results in a simpler bioprocess train with fewer unit operations, better pH control, reduced product inhibition from the organic acids, higher organic acid product concentrations and, most importantly, enhanced bioconversion rates and yields. The design and operation of SB-based organic acid processes are described, and the performance of representative processes investigated and demonstrated at bench-scale and pilot-scale tests are reported. The processes include enzymatic, anaerobic and aerobic fermentations to produce sorbitol, gluconic acid and succinic acid. Compared to conventional fermentation processes, SB processes show excellent productivity and high titers of the organic acid products. In long-term operational tests, SB processes were found to be robust with respect to fermentation contamination and membrane fouling issues. Finally, the technical and economic viability for commercial production of organic acids from biomass feedstocks using the SB technology is discussed.